ESTIMATING TIEDOWNS

TM 10-3930-673-10

F-7. LOADING RESTRAINT FACTORS (CONT)

Marine:

The Military Sealift Command (MSC) design LRFs are:

-1.2 in the lateral direction (relative to the ship)

-0.7 in the longitudinal direction

-0.2 in the vertical direction

MSC LRFs are for severe conditions

Actual marine LRFs vary. Marine tiedown restraint depends on the size of the ship (decreasing on larger vessels), the expected

sea state to be encountered, and the stow location of a given ship. Generally, the restraint required will increase for locations

high and forward (or aft) in the ship. The most severe conditions will occur on exposed "weather decks," where strong wind

and wet conditions add to the problem. A ship's crew may require additional lashing on exposed decks. Below-deck locations

that are closer to the vessel's center of gravity and rotation will experience less severe motion.

Air:

The USAF aircraft LRFs are:

-3.0 in the forward direction (relative to the aircraft)

-2.0 in the vertical direction

-1.5 in the aft and lateral directions

F-8. ESTIMATING TIEDOWNS

The number of lashings required to safely tie down the ATLAS for highway transport on a typical truck/semitrailer can be

estimated in the following manner:

Step 1- Determine the amount of longitudinal restraint needed. (With this method, the required vertical and lateral restraint is

covered by the longitudinal factors.)

-The highway loading restraint factor (LRF) is 0.7 (from Para 6-6) in the forward direction:

33,500 (ATLAS GVW) x 0.7 = 23,450 pounds

-The highway LRF is 0.3 in the aft direction:

33,500 x 0.3 = 10,050 pounds

Step 2-Determine the amount of chains needed.

-The angle to semitrailer deck and the angle to the angle to the side are assumed to be 45 degrees.

(cos 45 x cos 45 = 0.5)

-The SWL of the requisite 1/2-in. chain is 13,750:

= 3.4 (rounded up to 4)

Number of forward loading chains =

23,450

13,750 x 0.5

= 1.5 (rounded up to 2)

Number of aft loading chains =

10,050

13,750 x 0.5

F-9. FIGURES

The following figures present transportability data for the ATLAS.

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